1. Field of the Invention
The present invention relates to a subcooling-type condenser, and, more specifically, to a subcooling-type condenser, the header of which functions as a liquid tank.
2. Description of Related Art
In a refrigerating cycle, refrigerant compressed by a compressor usually is sent to a condenser. After the refrigerant is condensed by the condenser, the condensed refrigerant is sent to an evaporator through an expansion valve via a receiver tank, and after the cooling function is achieved at the evaporator by heat exchange between the refrigerant and an outside fluid, the refrigerant from the evaporator is sent to the compressor to again be compressed. In such a receiver cycle (i.e., a cycle having a condenser plus a receiver), vaporized refrigerant is not completely (i.e., 100%) re-liquefied, and a portion of the vaporized refrigerant remains as gas and the refrigerant is returned to the evaporator in this partially re-liquefied condition. Because a portion of the refrigerant remains vaporized, the cooling ability of the refrigerating cycle is limited.
In comparison with the above-described receiver cycle, recently a subcooling-type condenser has received attention. In a subcooling-type condenser, a heat exchange region of the whole of a core of a heat exchanger is divided into a refrigerant condensation core region, and a subcooling-core region for supercooling refrigerant condensed in the refrigerant condensation core region. In the subcooling core region, the remaining vaporized refrigerant is almost entirely re-liquefied, i.e., about 100%, by supercooling.
In such known subcooling-type condensers, a liquid tank is provided separate from a header of the heat exchanger. Usually, refrigerant from the refrigerant condensation core is stored in the liquid tank, and then the refrigerant is sent to the subcooling core.
However, in such a structure wherein the separate liquid tank is attached, the size of the entire subcooling-type condenser may be increased, and the number of parts and pipes may become large, thereby complicating the structure of the condenser. Although a structure is proposed wherein a liquid tank is structured integrally with a header of a heat exchanger, the inside structure of the header also may become extremely complicated, and the cost for manufacture may increase.
Further, Japanese Patent Publication No. JP-A-5-10633 discloses a condenser wherein a gas-liquid separating portion is provided between a refrigerant condensation core and a subcooling core. In this structure, however, because the gas-liquid separating portion occupies a relatively large area, the core size of the condenser, and ultimately, the size of the entire condenser may increase. Moreover, the structure of such a condenser may become still more complicated.
Accordingly, a need has arisen to provide a subcooling-type condenser having a desired re-liquefaction function, wherein a separately formed liquid tank is unnecessary. The condenser provides a liquid storing function in a header itself, which header has a simplified structure. This structure may reduce the size and cost of the whole of a condenser.
To achieve the foregoing and other objects, a subcooling-type condenser according to the present invention is herein provided. The subcooling-type condenser comprises a pair of headers, and a plurality of heat transfer tubes interconnecting the pair of headers and extending in parallel to each other. The condenser is divided into a refrigerant condensation core for condensing refrigerant and a subcooling core for supercooling refrigerant condensed by the refrigerant condensation core. A second header forming a header portion corresponding to an entrance portion of the subcooling core is formed integrally with a header portion for the refrigerant condensation core and a header portion for the subcooling core. At least the header portion corresponding to the entrance portion of the subcooling core is formed as a liquid refrigerant storage portion. A capacity of the second header Vh is set within a range of 100 ccxe2x89xa6Vhxe2x89xa6250 cc. Preferably, the capacity of the second header Vh is set within a range of 150 ccxe2x89xa6Vhxe2x89xa6200 cc.
The capacity of the second header Vh is set within a range, such that the compressor achieves an optimum width of a plateau region in a characteristic graph indicating a relationship between a degree of supercooling in a portion of the subcooling core and an amount of refrigerant enclosed in the subcooling-type condenser. The xe2x80x9cplateau regionxe2x80x9d refers to a region within which even if an amount of enclosed refrigerant (e.g., an amount of refrigerant present in a subcooling-type condenser) varies, the degree of supercooling in the subcooling core portion may be within a specified, relatively small range, for example, xc2x11xc2x0 C. In particular, the plateau region is a region, within which even if the amount of enclosed refrigerant increases or decreases, the respective portions in the subcooling-type condenser are substantially unaffected by varying conditions such as a high pressure. Consequently, a stable cooling operation is maintained. In the present invention, an optimum range of the width of this plateau region has been determined. In order to obtain this optimum range, the capacity of the second header having a liquid refrigerant storing function is set to the specified ranges described above. These ranges may correspond to the optimum ranges. The basis for determining the values for the upper and lower limits of these optimum ranges of plateau region is clarified by the explanation of the experimental results described below. Thus, in the present invention, an optimum liquid refrigerant storing function is given to the second header of the subcooling-type condenser, and the capacity of the second header is selected within the above-described optimum range.
Further, in the subcooling-type condenser according to the present invention, it is preferred that a capacity of at least the header portion corresponding to the entrance portion of the subcooling core in the second header is greater than a capacity of a header portion corresponding to an exit portion of the subcooling core in a first header. Particularly, it is preferred that the capacity of at least the header portion corresponding to the entrance portion of the subcooling core in the second header is within a range of about two times to about three times the capacity of the header portion corresponding to the exit portion of the subcooling core in the first header.
The second header may be formed, so that the cross-sectional area of the header portion for the refrigerant condensation core is substantially the same as the cross-sectional area of the header portion for the subcooling core.
The first header may be formed integrally with a header portion of the refrigerant condensation core and a header portion for the subcooling core. The refrigerant condensation core and the subcooling core may be separated by dividing the first header. In particular, the refrigerant condensation core and the subcooling core may be separated by providing a partition within the first header.
Further, in the subcooling-type condenser according to the present invention, a refrigerant passage comprising the plurality of heat transfer tubes in the refrigerant condensation core is formed preferably as a one-way path. In particular, refrigerant having passed through the refrigerant condensation core, which is formed as a one-way refrigerant path, is introduced into the subcooling core through the liquid refrigerant storage portion. The structure of the entire subcooling-type condenser may be simplified, and the condenser may be reduced in size, by forming the refrigerant path of the refrigerant condensation core as a one-way path. In the present invention, however, the refrigerant path of the refrigerant condensation core also may be formed as a two-way path.
Further, the subcooling-type condenser according to the present invention may be constructed, so that the pair of headers extend in a first or vertical direction, and the plurality of heat transfer tubes extend in a second or horizontal direction. The second header of the pair of headers also may be formed, such that the header portion of the refrigerant condensation core and the header portion of the subcooling core are integrally formed, and at least the header portion corresponding to the entrance portion of the subcooling core may be formed as a liquid refrigerant storage portion.
In the subcooling-type condenser according to the present invention, the liquid refrigerant storage portion is formed directly in the second header without providing a separate liquid tank, and refrigerant having passed through the refrigerant condensation core is introduced directly into the subcooling core through the second header. If the capacity of the header portion corresponding to the entrance portion of the subcooling core is greater than the capacity of the header portion corresponding to the exit portion of the subcooling core in the first header, and a liquid refrigerant storage portion having an adequate capacity is formed in the second header, the re-liquefaction of refrigerant may be accelerated without causing inconvenience, and the refrigerant may achieve substantially complete, i.e., about 100%, re-liquefaction.
Specifically, because substantially the same properties as those of a conventional liquid tank may be provided to the second header itself and because a part of the second header is formed as a liquid refrigerant storage portion, a desired re-liquefaction function may be achieved without substantially increasing the number of condenser parts. Consequently, the structure of the subcooling-type condenser may be simplified, the size of the entire condenser may readily be decreased, and the cost for manufacture may be reduced.
Moreover, in the present invention, because the capacity of the second header is selected within an optimum range, so that an optimum width of the plateau region may be achieved, a desired function for supercooling may be stably exhibited, and an efficient and stable operation may be achieved even for the cooling system as a whole.
Thus, according to the subcooling-type condenser of the present invention, refrigerant may be adequately re-liquefied in the subcooling core by forming a liquid refrigerant storage portion by the second header itself without providing a separate liquid tank. An optimum plateau region for stable operation of the condenser may be achieved by setting the capacity of the second header at an optimum capacity within a specified range. Therefore, a subcooling-type condenser having a simplified structure and desirable properties may be manufactured at a reduced cost, and the size of the entire condenser may readily be decreased.
Other objects, features, and advantages of the present invention will be understood from the following detailed description of preferred embodiments of the present invention with reference to the accompanying figures.